The formation of ice on the leading edges of aircraft engine inlets can occur during flight through clouds containing supercooled water droplets or during ground operation in inclement weather. Protection against ice formation is necessary since ice build-up near the engine inlet may obstruct the free flow of air into and around the engine adversely affecting engine performance. Additionally, damage may be caused to turbine blades or other internal engine components by chunks of ice breaking loose from the leading edge of the air inlet and entering the inlet airstream.
A typical inlet cowl anti-icing system has warm air introduced into a chamber within the leading edge of the inlet cowl. The anti-icing system keeps the inboard surface of the inlet cowl above freezing temperature and prevents ice formation that could interfere with engine performance. Spent air from the inlet cowl anti-icing system is often exhausted overboard without full utilization of the thermal energy contained therein, thereby wasting energy extracted from the engine's propulsion cycle.
The General Electric Company's unducted fan engine (UDF) operates with rotating blading both inboard and outboard of the inlet cowl and therefor requires anti-icing of the outboard surface of the inlet cowl in addition to the inboard surface as ice accumulation along the outboard surface may interfere with the airflow through the external blading or break loose and impact with the blading. Venting of spent anti-icing air overboard may also adversely affect the downstream structures or performance of the UDF engine.